To delete a new size on AliExpress, first log in to the AliExpress Seller Center and find the product whose size you want to delete on the product management page.

Click the Edit button to enter the Edit Product page, find the new size you want to delete in the Size option, select it and click the Delete button.

After confirming the deletion, save the changes and submit for review. After the review is passed, the new size will be successfully deleted. If you need to add the size again after deleting it, you can click the Add button in the Size option on the Edit Product page, enter the relevant information of the new size and save it. Remember to update the product information in a timely manner to ensure the accuracy of the size information.